1. Field of Invention
The invention relates to an embroidery data processing apparatus capable of producing sewing data used for forming underlying stitches in an embroidery area, and also relates to a method of producing embroidery data.
2. Description of Related Art
Conventionally, sewing data for forming stitches in an embroidery pattern was produced by determining coordinates of the positions where each needle is dropped. In recent years, an embroidery data processing apparatus has been developed and widely used which is able to semiautomatically produce sewing data for forming an embroidery pattern, by defining a set of embroidery data that specify the shape, position and size of an embroidery area, direction of stitches and thread density in the area, and the like. Where embroidering is performed to fill or cover the interior of a closed area with stitches, in particular, underlying stitches may be formed in order to make the embroidered area three-dimensional or swollen, and to prevent a work cloth from shrinking, or being drawn together by the stitches, as the embroidering operation proceeds. Thus, an apparatus for producing and processing sewing data for forming underlying stitches has been proposed and used in general. In a known method of producing such sewing data for forming underlying stitches, an underlying stitch area outline that defines the shape of an area in which underlying stitches are formed is produced or drawn inside a closed area that is enclosed by an outline for defining the shape of an embroidery area, and sewing data for forming underlying stitches is produced based on the underlying stitch area outline. Such a device is disclosed in U.S. Pat. No. 5,299,514, the disclosure of which is incorporated by reference herein.
If the known method of producing sewing data as described above is applied to the case where the outline defining the shape of the embroidery area intersects with itself at a point or points, however, the underlying stitch area outline defining the shape of the area in which underlying stitches are formed may be drawn outside the embroidery area, as shown in FIG. 10, thus making it impossible to produce sewing data for forming underlying stitches appropriately go.